Shock-absorber.



C. F. BRADBURN. SHOCK ABSORBER. APPLICATION FILED AUG 20, 1914.

Patented .rin 1, 1915.

s re ra ns new CFARLES FRANKLIN BRADBURN, OF DELMER, ONTARIO, CANADA.

SHOCK-ABSORBER.

Specification of Letters Patent.

Patented June 1, 1915.

- which, in a liquid filled cylinder containing a piston or doublepiston or plunger, the liquid may be made to offer piston, theresistance varying with the position of thepiston in the cylinder andthe direction of its motion. This resistance opposes-the motion of thepiston, within the cylinder, by exercising a retarding influence uponit, and may be made to vary within wide limits and at various rates ofincrease 7 piston within the cylinder.

and decrease in respect of the position of the ,7 By suitably connectingone portion of the mechanism, the piston by preference, to the body of avehicle, and the other portion of the mechanism, viz :the cylinder, tothe running gear, this varying resistance of the liquid may be utilizedto perform the functions of a shock absorber, 0., to prevent the suddencontracti on of the springs to their compression limits, or expansion totheir elastic limits, or beyond.

Gas may be employed as a resisting medium, but in this case, in additionto a retarding influence, there will be also a secondary acceleratinginfluence, due to the pressure gas gives under confinement or partialconfinement, because of its elasticity, and in these specifications Ishall limit my "description of the operations of the invention moreparticularly to the case in which a liquid is used as a medium, and ofliquids, oil will possess advantages.

Then the running gear of a vehicle encounters a sudden elevation in theroadway it rises and momentarily compresses thesprings, against theweight of the body of the vehicle, which immediately expand and lift thevehicle body from its normal position with relation to the running gear.Owing to the compression of the springs resulting from the inertia ofthe body, the pistonwill reach the lower limit of its strokewithin thecylinder. Following this, the body of the vehicle will rise under theelasticity of acontrollable ,variable resistance to the movement of theits springs, and be carried to a point or plane higher than thatrepresented by the simple elastic limit of its springs; during .which,the piston will rise to the upper limit of its stroke. Following thismovement, the body of the vehicle will fall under gravity and theretractive action of the distended springs, the latter again reachingtheir mid position, and the piston of the mechanism its mid position inthe cylinder.

The movement outlined is an extreme or primary movement which willalways be followed by secondary movements or oscil lations, due to thereaction of the inertia or weight of the body and the elasticity of thesprings. For simplicity sake, we will treat these movements asconstituting a simple rise and fall of the piston within its cylins der.The half stroke or mid position will correspond or approximate at leastto the normal position of the springs, that is, their position when thevehicle is at rest under its weight and normal load.

The design roughly depicted herein is one either end of the cylinder,the maximum resistance being attained by further displacement of theliquid becoming impossible as the piston reaches either limit of itsstroke; a slighter resistance occurring the instant of reversal whichrapidly decreases as the piston moves inwardly or toward itsmid-position, becoming negligible at points nearer the limits of itsstroke than the points at which negligible resistance ceases, when thepiston moves outwardly from its mid position.

Different resistances, both in respect. to the amount of resistanceopposed to the piston and to the rates of variation, having regard forthe pistons position and direction of advance, may be obtained byvariations in the details of the construction of the cylinder to meetany practical case required, within the limit of engineering practice.

verse with the mid the connecting block Z.

have bolt holes suitable for the attachment tions nsverse s ation, l thecylinder and one of ic heads; Fig. 3, shows a perspective view of thedoable. piston or plunger.

Like characters of reference refer to like parts throughout thespecification-and drawings.

a is a cylinder having cylinder heads a and a. The head afis removable,and the head a" carries a connecting block 1.

b is a removable lining, containing a groove or several similar groovesit, forming a by-pass, or Icy-passes for the liquid from one side to theother of'the piston.

72 represents the middle point, or transplane of the ,cylinder, andcoincides position or half stroke of the piston.

79' and 79 represent points or transverse planes, equidistant from paboveand below respectively, while 9 and g are points or transverseplanes beyond and p, and also equidistant from'p, and from theirrespective ends of the cylinder, the distance p-,g .or 7) g beingslightly less than the extreme length of the piston to be described.

The groove h is of varying cross section, and is greatest between thepoints 1) and p". From p outwardly and upwardly, the cross section ofthe groove gradually decreases, and the groove terminates at (7,similarly from .the point p outwardly, or

downwardly, the groove tapers or dimin-' ishes in crossesection andterminates at '9. These points 9 and 9 mark the limits of the pistonstroke.

a is the'piston, or double piston, two like heads a and a" separated andinclosing a space of chamber Jr. Thus the cyli inder is madeto containthreespaces or chambers k, k" or is"; within the piston head; is above,and lc below the piston head, liquid resisting medium.

d is the piston rod carrying the piston head a at its lower end and atits upper-end. These blocks Z, Z

of clips or such devices as may be used to effect connections withthebody and running gear of a vehicle, or with opposing porof thevehicle springs, but no particular type of connections is shown here,since these will vary greatly in different types of vehicles. The pistonrod d isth-readed at its lower end and extends through borings in thepiston heads 0 and, 0"; the head a being held in place by the threadedcollars or nuts e and 7 while the head a is held by heads may be .diumfrom thespace k having I all spaces being kept filled'with theshould besuch that at the end which and should be i is, 1f we take point e mits apassage or flow resisting meto the space I 1 ever there is an excess ofpressure space in over that in the space is. Sh the valve 9'' opens intothe space 70 whenever there is an excess of pressure in the space While,if there is a defect oi ressure in is, in respect of k, the valve g willbe held closed, or if the pressure in is is in defect of is, the valve 9will be closed.

traveling toward the upper end of the cylinder, the valve gfvvill beheld closed, and when moving toward the lower end or the cylinder, thevalvelg will be closed. When the piston starts on the. down stroke, thevalve 9 will open at the instant of reversal, and remain open at leastuntil the entire length of the piston is alongside the broad ened'partp-p, of the groove h, and similarly, when the piston rises, the valve 9'will open at the instant ofreversal, and reterbalance its weight, butthe valve 9 does not require a spring unless the mechanism be used insome unusual adaptation in a hori-' zontal position, in which case,both'valves Will needsprings to compensate for their inertia if thehighest balance in operation be desired.

The piston a, in respect-of the groove it, acts as its own valve tocontrol the flow of the medium across the edges of its heads from anyone chamber or space to any other or-others, and the extreme length ofthe piston, that is, its length in maximum spacing of a full stroke, theinner edge orface of the inner piston head should fall slightly withinthe tapered 'part of the groove corresponding to the particular end ofthe cylinder at the piston may be, that is, should pass the points 30and p in the outward travel. By inner piston head is meant theparticular head that, at this phase of the cycle, lies toward the planep, and by inner face llVhen the piston is meant that face of the samewhich bounds i Liaalo as to position within the cylinder in the firstcase, and in the last case, to position upon or within the double pistonhead. The cylinder is provided with a small reservoir m havi'ng a ,forcescrew 72, by which, when a stop cock 0 is opened liquid may be forcedinto the cylinder to refill it and then compensate for anv losstherefrom. From the foregoing description the full operation of themechanism will now be easily understood.

Let the piston be connected with the body of a vehicle and thecylinderwith the running gear. Let the springs of the vehicle beat midposition with the piston of the mechanism at mid position or the point79.

Let the movement of the piston be con-' sidered as a simple rise andfall within the "cylinder and let the-extreme case be taken, viz:-thatin which the piston moves to the limits of its travel and completes twofull strokes. Then as the piston falls toward the end a" of the cylinder(1, there will obtain an 'excess of pressure of liquid in the space '76over that in the spaces 70 and 7c, the valve 7' will remain closed and aflow of liquid will occur from the space-7v" to the space k through thegroove it across the edge of the piston head 0" and thence to the spaceit through the groove 11, across the edge of the head 0. The valve g mayopen, but this is immaterial, the determining factor of resistance beingthe cross section of the groove h directly in line with the, outer oradvancing surface or face of the piston head 0'. The resistanceencountered by the piston however will, owing to the large cross sectionof the groove, be practically negligible until the advancing face of thepiston c" registers with the point p,thence an increasing resistancewill set in and this will attain a maximum as the advancing face of thepiston registers with the point g and cuts off the flow, from k, thispoint marking the limit of the downstroke and the imprisonment of aportion of the liquid in the,

lower end of the cylinder to cushion the blow.

On the upstroke at the instant of reversal the advancing face of thepiston 0 meets an unbalanced pressure in the space is which causes "aflow of the medium from the space 7: to the space k through the groove hand thence into the space is, this excess of pressure being transmittedto the, space is or chamber of the double piston and causing the valveg'to open and allow a flow through the passage 1" and into the space is.The valve 9 will not be opened as the pressure of I; cannot at thisphase exceed the pressure within is and hence the controlling factor ofresistance will be the cross section of that particular portion of thegroove h that may lie directly in line with the inner or retreating faceof the piston head f; that is.

c which bounds the central chamber, the magnitude of the above crosssection being the measure of the flow from the space 7/ to the space Aand thence to the space la. As the retreating face of 0' above mentionedmoves across successively greater cross sections of the tapering portionof the groove, the resistance diminishes and when this face registerswith the point or plane y)" the resistance becomes a minimum andpractically negligible and remains so until the advancing face of 0reaches the point 1). From this forward, the resistance increases, thedetermining factor being the magnitude of the cross section of thegroove that for the instant registers with the advancing face of thepiston in this phase of its upward stroke or travel. When the said facereaches the point 9, the resistance attains its maximum, the flow is cutoff and a portion of the liquid is imprisoned in the upper end ofcylinder to cushion the blow in like manner to the action described asresulting when the piston terminated its antecedent downward halfstroke. Then finally, in brief, as the piston reverses its motion andtravels downward to the mid position plane p and to the completion of afull primary cycle or two complete strokes, there will be a flow from kto is through the groove h and thence mostly through the valve g to thespace 7a while the valve 9 willbe held closed. The resistance factor,similarly to the corresponding case, before described, will bedetermined by the-magniloo tude of the particular cross section of thegroove it that may from instant to instant register with the retreatingsurface or face of the piston head c; that is the face 0" which boundsthe space 70 or piston chamber. This resistance as before, decreasesuntil the above face registers with the point p and from this forward tothe completion of the full cycle or return'of the piston to the midposition 19, the said resistance is at a mini mum.

The description of the action of the secondary oscillations orincomplete strokes will be obvious, and, in short, as the piston movesacross the central transverse planes of the cylinder, the resistance isa minimum, and as it.approaches either end, an increasingresistance setsin and gradually becomes a maximum terminating the full strokes of thepiston, While as the pis- 20 ton reverses its motion at either the upperor lower limiting positions a considerable resistance is encounteredwhich, as the piston travels toward mid position, soon decreases to aminimum and remains so while the travel of the piston is across theaforesaid middle portions of the cylinder; that is, while the doublepiston in its entire length is moving alongside the broadened portion ofthe groove. The spaces through which that face of 1 its stroke,

30 inertia of a increasing'resist 2e acts as the piston vane-es toward rend of the cyll' much greater tin the spaces through decreasingresistance acts as the pisw 5 cedes from either end of the cylinder. econnection between the action of the anisrn and the movements vehiclebody and its running gear and the relationship to the reactions of theinertia ofa body and 1c ,of the elasticity of its springs are nowsufficicntly evident not to require further description. A single pointmay be noted, when the piston spaced and the extreme stroke madeshorter, the recessional or recedingresistances are small, and when thespacing of the piston heads is least and greatest, the resistances aregreat, that is, are small'and great, having regard for thefull orextreme strokes. 4

A The advantages of a construction of this kind for shock absorbingpurposes are plain, inasmuch asit furnishes a control in respect toresistances that cannot be duplicated in any -'system of springs. Manyshock absorbers do notrelieve the springs of a vehicle either from unduecompression or distention. The bouncing efi'ect ofs'pringsisparticularly well taken care of, so that the vehicle body does not tendto jerk up, the running gear, and allow, -in,,- the case of anautomoblie, the tractionwheels a) lose. their.v grip and cause racingqor skidding. I 1

If the resisting medium employed be air, or other gaseous mixture orgas, the invention possesses many advantages, as We may imprison' in theends of the cylinder sufiicientgas to cushion the piston at the end ofbut not enough to bounce it, as in the case of a mechanism in which allthe gas, or at least half the'conten'ts of the cylinder iscompressedalternately in the ends of the cylinder. Of .course, in usingthis mechanism as a-pneumagtic or gas shock absorber, the passages willneed to be much larger and although the general design willremainunchanged, the particular proportions of parts will requiremodification. 1 Having thus fully described the nature of my invention,what Iclaim as new and desire to secure by Letters Patent, is 2-- 1. Ashock absorber comprising a liquid filled cylinder, said pistoncontaining a chamber, having ports with valves opening outwardly, thecylinder having a longitudinal groove of a varying cross section, tocause the liquid heads are most widely,

the extreme stroke made ing a removable lining,

and a double piston therein,

to offer a variable resistance to the motion of the piston relatively tothe cylinder.

A. shock absorber comprising a liqu' lcylinder, and a doubie piston therpiston containin a chamber, havi' as with valves opening outwardly, tinder a longitudinal groove of section, to cause the liquid'to I yingcross a variable resistance to the motion or the piston relatively tothecylinder, this re sistancebeing negligible as the piston moves ron1 itsmi position outwardly across middle transverse planes of the cylinder.but increasing as the piston approaches the lir it of its extremestrokes and reaching a maximum thereat, this resistance rapidlydecreasing When the piston reverses its motion at either of these limitsand becoming negligible when the piston travel inwardly toward itsmid-position or mid stroke. v

3. A shock absorber comprising a liquid filled'cylinder, and a doublepiston, said piston containing a chamber, valves opening outwardly, thecylinder havinga longitudinal groove of a varying cross section, tocause the liquid to ofi'er a variable resistance to the motionof thepiston, and in such manner that the resistance is practically.negligible as the piston moves across the middle 7 creasingas the pistonapproaches the limits portions of the cylinder, but inof its extremestrokes, and, as the piston reverses its motion to recede tomid-position, capable either of rapid or of instant decrease tonegligible. proportions.

. 4:. A shock absorber comprising a cylinder, and a piston therein, saidcylinder havhaving 'a lengthwise groove of variable cross section, andsaid piston having a chamber with ports controlled by outwardly-openingvalves.

5. A shock absorber comprising a cylinder, and a piston therein, saidcylinder havcontinues its having parts with ing a lengthwise groove ofvariable cross U section, and said piston having a chamber with portscontrolled by outwardly-opening valves.

y 6. In a shock absorber compris nga liquid filled cylinder and a doublepistoma'rheans of varying the length of the ext-remelstrokes throughvariation in the spacing of the piston heads. v Toronto, duly 17th,"1914.

, CHARLES return- Signed in the presence of-- C. H. ICHES,

.EDWARD S. BERNSTEIN.

BADBURN.

